This is Alec. He is a goalie for his soccer team. He is allergic to wasps.
Alec dives to save the ball and lands on a wasp which stings him. He thinks that he just landed on a prickly weed and keeps playing.
One minute later Alec starts getting hives all over his body and it gets hard to breath. He runs over to his mom and she calls an ambulance, she had forgotten his epi-pen at home. An epi-pen is something you use to get a burst of adrenaline or epinephrine, depending on your allergy, when having an allergic reaction.
Alec faints and is given a dose of adrenaline to open his airways. He is then taken to the hospital where he is stabilized and admitted for a few days to be observed.
While at the hospital Alec asks the doctor to explain what happened to him.
When the wasp stung him its stinger pierced the human body's first line of defense, the skin. The skin is also the first mechanism of non-specific immunity of the human body. Non-specific means that they defend against every invader of the body. The wasp venom was delivered straight to the bloodstream.